The present invention relates to a shell structure particularly usable in ski boots.
Ski boots are currently usually composed of elements, such as the shell and the quarters, obtained by injection-molding thermoplastic material.
In particular, the manufacture of the shells requires the intervention of personnel after the molding has been performed in order to remove said shells from the mold.
Furthermore this operation must be immediate, since the shell has a structure which defines a narrowing at the foot instep, so that it is necessary to make use of the elastic deformation of said structure while it is still warm in order to remove it.
For this purpose machines are used having programmed motions, with the disadvantage of having to solve problems such as the centering of said machines with respect to the mold and the presetting of the machine's motions on three axes.
Due to the semi-closed configuration of the shell, it is furthermore necessary to use personnel to assemble its internal components, constituted by pressers, mechanical elements connectable to levers, and others.
Another disadvantage for the industrialization of ski boots resides in the fact that it is necessary to prepare a mold for each size in the range, increasing overall costs and entailing the selection of the size range to be offered to the public.
To this respect, the U.S. Pat No. 4,308,674 describes a monolithic front-entry ski boot composed of a shell, in which a soft inner shoe can be inserted, and of an element which is rearwardly associable with said shell and includes a quarter which embraces the rear part of the leg.
The sole of the shell is furthermore rearwardly provided with a pocket-shaped seat for coupling to said element, the locking therebetween occurring by means of downwardly arranged screws. The French Pat. No. 2,358,117 also describes a ski boot which allows the user to easily vary the size of the boot as the foot grows, this being a problem particularly felt in children's boots.
The main disadvantage observed in said known boots resides in the fact that the coupling provided by means of the pocket-shaped seat does not ensure an axially oscillation-free coupling between said element and said shell.
The element which can be rearwardly associated with the shell furthermore has a quarter which cannot be used for the entire range as it is a characterizing part of the boot.
Finally, the coupling region is furthermore visible, making the boot aesthetically unpleasant.
The fact is also stressed that the hypothetical size change can be achieved directly by the customer and cannot be univocally preset by the manufacturer.